1, the circuit board debugging parameters
PCB design and PCB copy board work, often to the board for debugging tests. Six modules PCB board debug debugging which is often encountered in one . In order to facilitate a better understanding of the six modules PCB debugging techniques , we first briefly what is six modules . The six modules are the core components of the circuit board , its design structure , production process, largely determine the performance of the product. Standard six modules is EIA / TIA 568B.2-1, the most important parameter is the insertion loss, return loss, near-end crosstalk and the like.
Insertion loss (Insert Loss): due to the transmission channel impedance is present, it increases as the signal frequency , the high frequency components of the signal leaving the increased attenuation , the attenuation and the frequency signal is not only , but also with the transmission distance. As the length increases , the signal attenuation increases . With a number of signal loss along the transmission path to measure the length of the unit , showing the source signal is passed to the transmitter side ratio of the received signal strength .
Return Loss (Return Loss): Due to a change in impedance will produce localized shocks, resulting in signal reflections . Is reflected in the transmitting side will form part of the noise energy , resulting in signal distortion , and lower transmission performance. As a full-duplex Gigabit Ethernet , the reflected signal will be mistaken for a signal received useful signal fluctuations caused by , resulting in confusion. Less energy is reflected , means that the channel used by the line impedance consistency better, more complete transmission signal , the smaller the noise on the channel. Return loss is calculated RL : The Return Loss = transmit signals ÷ reflected signal .
In PCB design, to ensure the consistency of the impedance of the whole line , and six with 100 ohm impedance cable tie , is the way to solve the return loss parameters of failure. For example, the distance between the layer PCB uneven lines , transmission line copper conductor cross-section changes , six cable conductor and a conductor within a module mismatch , etc., will lead to the return loss parameters .
Near-end crosstalk (NEXT): NEXT refers to a pair of transmission lines , a pair of wire -to-wire signal coupling to another , that is, when a line when you send a signal to the other line to receive a neighboring signal. This is mainly due to the approaching signal crosstalk coupling came about through capacitive or inductive . How to reduce the capacitive or inductive coupling of the signal over ? Typically by way of compensation , offset the reduced interference signal , it can not produce a standing wave , is the main way to solve the failure parameters .
2 , the core technology and the failure mechanism
Korea based mainly on the following explanation of a company over the course of six modules PCB prototype , a very important reference value. In the trial phase of the module , using theory to guide to computer-aided design as the basis, quickly achieve the desired results . PCB design in six modules conducted in our country , mainly in diagonal lines made based compensation theory , a lot of trial work , too, can achieve the desired results .
